THE DISEASES OF WINE 135 



acetic acid which it has formed. But, as usual, Pasteur 

 was deceived only half way, and his deduction was exact. 

 The vitiations in taste which sometimes are observed in 

 certain wines could not result from any normal physical 

 or chemical phenomenon, for the wine was preserved 

 almost everywhere in the same fashion, and these 

 changes ought to be seen everywhere. There remained 

 then one plausible explanation, that is that these vitia- 

 tions came from special fermentations, produced by 

 special ferments analogous to the acetic ferment. 



Here is the conclusion to which the logic of his mind 

 and of his acquired knowledge led Pasteur! It re- 

 mained to see what experimentation would show. He 

 had at Arbois, fortunately, some old comrades of his 

 childhood who owned some caves well stocked for home 

 and market purposes, and he easily obtained permission 

 to subject their wines to a microscopic study. 



From the first moment, he surmounted the difficulty. 

 Every time that the tasters pointed out to him a par- 

 ticular defect in taste, he found so constantly a distinct 

 microscopic species mixed with the yeast in the bottom 

 of the cask, that soon he was able to make the test in- 

 versely, that is to say, to indicate in advance the savor of 

 the wine by examining its deposit. The normal wines 

 contained only the yeast. 



With a guiding idea, so clear and so well verified by 

 experiment, he could begin. After some months passed 

 at Arbois in an improvised laboratory, Pasteur succeeded 

 in elucidating the question, and, in 1866, he was able to 

 place in the hands of the Emperor, who had encouraged 

 him in his researches, a book containing the complete 

 solution of the problem which he had set himself to solve. 



This book is a trilogy, of which all the parts hold to- 

 gether. In the first part, he shows that all the maladies 

 enumerated above, the turning, becoming bitter, becom- 



